Added support for flipping from Freebase pages to dbpedialite.

dbpedialite.rb

@@ -219,6 +219,13 @@ def format_iso8061(datetime)
       redirect_from_title($2)
     elsif params[:url] =~ %r{^http://dbpedia.org/(page|resource|data)/(.+)$}
       redirect_from_title($2)
+    elsif params[:url] =~ %r{^http://www.freebase.com/(view|inspect|edit/topic)(/.+)$}
+      begin
+        data = FreebaseApi.lookup_by_id($2)
+        redirect "/things/#{data['key']['value']}", 301
+      rescue FreebaseApi::NotFound
+        not_found
+      end
     elsif params[:url] =~ %r{^http://([\w\.\-\:]+)/(things|categories)/(\d+)$}
       begin
         data = WikipediaApi.page_info(:pageids => $3)

lib/freebase_api.rb

@@ -7,6 +7,12 @@ module FreebaseApi
   RDF_BASE_URI = URI.parse('http://rdf.freebase.com/rdf/')
   HTTP_TIMEOUT = 2
 
+  class Exception < Exception
+  end
+
+  class NotFound < FreebaseApi::Exception
+  end
+
   def self.mqlread(query)
     uri = MQLREAD_URI.clone
     uri.query = 'query='+CGI::escape(JSON.dump({'query' => query}))
@@ -22,14 +28,18 @@ def self.mqlread(query)
     # Throw and exception if the JSON response was unsuccessful
     data = JSON.parse(res.body)
     unless data['code'] == '/api/status/ok'
-      raise "Freebase query failed: #{data['messages'][0]['message']}"
+      raise FreebaseApi::Exception.new("Freebase query failed: #{data['messages'][0]['message']}")
+    end
+
+    if data['result'].nil?
+      raise FreebaseApi::NotFound.new("Freebase query failed return no results")
     end
 
     data['result']
   end
 
   def self.lookup_wikipedia_pageid(pageid, language='en')
-    data = mqlread({
+    mqlread({
       'key' => {
         'namespace' => "/wikipedia/#{language}_id",
         'value' => pageid.to_s,
@@ -41,11 +51,21 @@ def self.lookup_wikipedia_pageid(pageid, language='en')
        'guid' => nil,
        'limit' => 1
     })
+  end
 
-    if data.nil? or data['mid'].nil?
-      raise "Failed to lookup wikipedia page id"
-    end
-
-    data
+  def self.lookup_by_id(identifier, language='en')
+    mqlread({
+      'id' => identifier,
+      'key' => {
+        'namespace' => "/wikipedia/#{language}_id",
+        'value' => nil,
+        'limit' => 1
+      },
+      'name' => nil,
+      'mid' => nil,
+      'guid' => nil,
+      'limit' => 1
+    })
   end
+
 end

spec/dbpedialite_spec.rb

@@ -237,7 +237,7 @@ def app
       )
       FakeWeb.register_uri(
         :get, %r[http://www.freebase.com/api/service/mqlread],
-        :body => fixture_data('freebase-mqlread-ceres.json'),
+        :body => fixture_data('freebase-mqlread-934787.json'),
         :content_type => 'application/json'
       )
     end
@@ -340,7 +340,7 @@ def app
         )
         FakeWeb.register_uri(
           :get, %r[http://www.freebase.com/api/service/mqlread],
-          :body => fixture_data('freebase-mqlread-ceres.json'),
+          :body => fixture_data('freebase-mqlread-934787.json'),
           :content_type => 'application/json'
         )
         header "Accept", "text/plain"
@@ -692,6 +692,26 @@ def app
       end
     end
 
+    context "flipping from a Freebase page" do
+      before :each do
+        FakeWeb.register_uri(
+          :get, %r[http://www.freebase.com/api/service/mqlread],
+          :body => fixture_data('freebase-mqlread-en-new-york.json'),
+          :content_type => 'application/json'
+        )
+        get '/flipr?url=http%3A%2F%2Fwww.freebase.com%2Fview%2Fen%2Fnew_york'
+      end
+
+      it "should redirect to the coresponding Dbpedia lite thing page" do
+        last_response.status.should == 301
+        last_response.location.should == 'http://example.org/things/645042'
+      end
+
+      it "should be cachable" do
+        last_response.headers['Cache-Control'].should =~ /max-age=([1-9]+)/
+      end
+    end
+
     context "flipping from an unknown page" do
       before :each do
         get '/flipr?url=http%3A%2F%2Fwww.bbc.co.uk%2F'

spec/fixtures/freebase-mqlread-en-new-york.json

@@ -0,0 +1,15 @@
+{
+  "code":          "/api/status/ok",
+  "result": {
+    "guid": "#9202a8c04000641f80000000002f8906",
+    "id":   "/en/new_york",
+    "key": {
+      "namespace": "/wikipedia/en_id",
+      "value":     "645042"
+    },
+    "mid":  "/m/02_286",
+    "name": "New York City"
+  },
+  "status":        "200 OK",
+  "transaction_id": "cache;cache03.p01.sjc1:8101;2012-05-06T21:48:31Z;0052"
+}

spec/freebase_api_spec.rb

@@ -6,12 +6,12 @@
     before :each do
       FakeWeb.register_uri(:get,
         %r[http://www.freebase.com/api/service/mqlread],
-        :body => fixture_data('freebase-mqlread-ceres.json')
+        :body => fixture_data('freebase-mqlread-934787.json')
       )
       @data = FreebaseApi.lookup_wikipedia_pageid(934787)
     end
 
-    it "should not return a Hash" do
+    it "should return a Hash" do
       @data.should be_a(Hash)
     end
 
@@ -32,6 +32,44 @@
     end
   end
 
+  context "looking up the Wikipedia Pageid for a Freebase identifier" do
+    before :each do
+      FakeWeb.register_uri(:get,
+        %r[http://www.freebase.com/api/service/mqlread],
+        :body => fixture_data('freebase-mqlread-en-new-york.json')
+      )
+      @data = FreebaseApi.lookup_by_id('/en/new_york')
+    end
+
+    it "should return a Hash" do
+      @data.should be_a(Hash)
+    end
+
+    it "should return the name of the topic" do
+      @data['name'].should == 'New York City'
+    end
+
+    it "should return the GUID for the topic" do
+      @data['guid'].should == '#9202a8c04000641f80000000002f8906'
+    end
+
+    it "should return the Machine ID for the topic" do
+      @data['mid'].should == '/m/02_286'
+    end
+
+    it "should return the Freebase ID for the topic" do
+      @data['id'].should == '/en/new_york'
+    end
+
+    it "should have a key for the English Wikipedia page id" do
+      @data['key']['namespace'].should == '/wikipedia/en_id'
+    end
+
+    it "should return the Wikipedia page id" do
+      @data['key']['value'].should == '645042'
+    end
+  end
+
   context "lookup up a Wikipedia pageid that doesn't exist in Freebase" do
     before :each do
       FakeWeb.register_uri(:get,
@@ -43,7 +81,7 @@
     it "should throw an exception" do
       lambda do
         FreebaseApi.lookup_wikipedia_pageid(4309010)
-      end.should raise_error(RuntimeError, 'Failed to lookup wikipedia page id')
+      end.should raise_error(FreebaseApi::NotFound, 'Freebase query failed return no results')
     end
   end
 
@@ -58,7 +96,7 @@
     it "should throw an exception" do
       lambda do
         FreebaseApi.mqlread(:foo => :bar)
-      end.should raise_error(RuntimeError, 'Freebase query failed: Type /type/object does not have property foo')
+      end.should raise_error(FreebaseApi::Exception, 'Freebase query failed: Type /type/object does not have property foo')
     end
   end